function res = Lax_Wendroff_onestep(u,N,mu,x_max,a)
h = x_max/N;
u = fill_ghostcell_period(u,N,1);
res = u(2:N+2) - 0.5*mu*(u(3:N+3)-u(1:N+1)) + 0.5*mu*mu*(u(3:N+3)-2*u(2:N+2)+u(1:N+1))+a*mu*h*u(2:N+2);